They are not dumb questions. You'd be surprised how often they show up on this forum. They are perfectly logical.
Since yours are 18 weeks old, I'd get them in now. They probably won't start laying for a bit yet, but they could start any time. If you have problems with them such as the chickens sleeping in them instead of on the roosts or maybe they are scratching the fake eggs and nesting material out, you have time to correct the problem.
There is a pretty good chance the first egg or two will just show up anywhere. Often with a young pullet just learning to lay, it seems that the first egg or two surprises them and they don't realize what is happening. But when they get some control of the situation, they start looking for a safe place to lay. You want that first controlled egg in a nesting box since they are creatures of habit and can get in some bad habits about where to lay about that time. Some do have control from the first egg, but don't panic if one is under the roost or just on the floor.
Put a fake egg in the nest. Golf balls work great, but you can use anything the size and shape of an egg. Ping pong balls and those plastic Easter eggs work but are pretty light and can easily get scratched out. I half filled plastic Easter eggs with sand and glued them shut, and that worked, but I eventually switched to golf balls. Chickens like to lay where other chickens are laying. I guess they think that if another hen thinks it is safe and the egg has not been eaten yet, it is a safe place to lay. I strongly recommend a fake egg. It does make a difference.
I find that I need a lip across the bottomn of the nesting box about 5" to 6" high to keep them from scratching out the nesting material or eggs, fake or real. From some of the photos on here some others apparently don't have that problem. Maybe mine are just energetic scratchers that like to rearrange the nesting material regularly.
Good luck and get ready. You will soon enjoy that first egg.
lol
